Osteoporosis and keel bone fractures affect the majority of commercial laying hens, causing chronic bone pain that is one of the most significant but underrecognised welfare problems in the egg industry.
Keel bone fractures cause chronic pain that significantly impairs laying hen welfare throughout the productive life of the bird. The evidence that fractures cause pain is supported by behavioural studies showing altered posture, reduced movement, and modified behaviours consistent with pain avoidance in fractured birds. The surprising finding that free-range hens have comparable fracture rates to caged hens — due to collision with perches and landing from height — has complicated welfare communication around housing system choices. The most effective interventions are those that address perch design, landing areas, and genetics rather than simply housing type. Keel bone welfare is now a major focus of layer welfare research and breeding programmes.